Unique pattern of R-gene variation within populations in Arabidopsis

An understanding of the variation pattern in disease resistance (R) genes is essential for its use in breeding programs aimed at neutralizing the threat of pathogens. Although the variation between populations is well known, there is little research about R-gene variation patterns within populations. Here, we investigate the polymorphism at three R-gene loci of 39 individual plants from nine populations of Arabidopsis thaliana. Our data suggest that alleles of each locus from individuals within a local population were either nearly identical, or highly diverse as ones between populations. The vast majority (92.5%) of within-population variation was shared globally, with high levels of allelic diversity (up to 11.7%) and abundant diverse-alleles. This unique pattern of within-population variation at R-loci suggests that individual plants within a population had the great potential to maintain a high level of globally-shared polymorphisms, and that the diversifying selection was the major force maintaining such polymorphisms. Consequently, the shared-polymorphism became recyclable for new R-genes, as the corresponding avirulence re-emerges in pathogen populations.

了解抗病（R）基因的变异模式，对于将其应用于旨在应对病原体威胁的育种计划至关重要。尽管种群间的变异已广为人知，但关于种群内R基因变异模式的研究却很少。在此，我们对来自9个拟南芥种群的39株个体植物的3个R基因位点的多态性进行了研究。我们的数据表明，当地种群内个体的每个基因座的等位基因，要么几乎相同，要么像种群间的等位基因那样高度多样。种群内变异的绝大多数（92.5%）在全球范围内是共享的，具有高水平的等位基因多样性（高达11.7%）和丰富的不同等位基因。R基因座上这种独特的种群内变异模式表明，种群内的个体植物极有可能维持高水平的全球共享多态性，并且多样化选择是维持这种多态性的主要力量。因此，当病原体种群中相应的无毒基因再次出现时，共享多态性可循环用于新的R基因。